Process for cracking oils



Feb. 6,1943. C. W. TYSON ET AL 2,311,318

PROCESS FOR CRACKING OILS l Filed oct. 15, 193s 3 sheets-sheet i I I. ,yf/77- Exava/vaff call. 1 @E erop' l WMF/,51E3 5NK CoA/awr 42 I u TRUE' COA/OUI 7" CON /7 Q1 617.5 Wim/I? INLET Feb. i, 1943: c. w. TYsoN ET-AL 2,3115318 PROCESS 'FOR CRACKIG OILS f/EA 7' EXC'HA NGER K WMI 93,

SPE/v7 #Mmmm/olv Gas l I 4| -Il- -79'24 if Feb. 1.6,l 1943. C, w, yTYSON AL v 2,311,318

PROCESS FOR CRACKING oILs A y Filed 001". 15,' 1958 5 Sheets-Sheet 3 Al w.

REc/ncuLHf//IG CONDUIT FRA Tlc/VA TMG To W5! @zal f '159 Patented Feb. 16, 1943 2,311,318 raocEss Foa casema oms Charles W. Tyson and Eger V. Murphree, Summit,

, and Herbert G. M. Fischer, Westileld, N. J.,

assignors to Standard Oil Development Gompany, a corporation of Delaware Application October 15, 1938, Serial No. 235,232

Claims.

This invention relates to a method of carrying out reactions in the presence of solid contact materials which become fouled with carbonaceous deposits which must be periodically regenerated to remove such deposits. The invention pertains more particularly to a process for accomplishing the reaction and regeneration of the contact mass alternately in the same 'reaction chamber.

While our invention in some of its broadest aspects will have a broader application as `will appear hereinaitenit is particularly adapted for the catalytic conversion of hydrocarbon oil in the presence of solid adsorbent contact material. During this conversiontreatment, the surface of the contact mass becomes fouled more or less rapidly with carbonaceous deposits which reduce the activity of the contact material and nally necessitates discontinuance of the process. The

' activity of this contact material may be restored by subjecting it to a regenerating treatment which will remove such carbonaceous deposits. This can be accomplished by passing an oxidizing gas, such as air or air in admixture with diluent gases. such vas steam or combustion products, through the catalyst bed to burn the carbonaceous deposits therefrom.

When regenerating in this manner. it has been found that with certain types of materials, such as adsorbent clays, excessive temperatures during the burning operation tend to reduce permanently the activity of the catalyst.

lSince the regeneration of the catalyst is a highly exothermic reaction, diiiiculties have been encountered in maintaining the proper temperature control during the regenerating period.

In processes of this character involving periodic regeneration of the contact mass, it is considered more economical to carry out the regeneration in the same chamber in which the reaction is accomplished so as to avoid the additional expense required to transferthe mass to and from the reaction chamber. When carrying out the re-l generation withinthe reaction chamber, however,

the reaction period must be periodically interrupted for a time suilicient'to accomplish the regeneration. This results in a reduction in capacity of the equipment to produce a given amount of desired product within a given time. It will therefore be apparent that capacity of the equipment is limited by the time required to accomplish the regeneration and it is desirable to reduce the regenerating period to a minimum.

In operations involving alternate reacting and regenerating periods of the character mentioned,

the conditions maintained during the two periods dIIIer widely. For example, during the catalytic cracking of hydrocarbon oils, the velocity of gases passing through the contact mass under optimum conditions is of a different order than the velocity cf regenerating` gases necessary 1.o accomplish rapid regeneration. As a further example, during the cracking'p'eriod there is a consumption of heat due to the endothermic heat of reaction whereas during the regenerating period a large 5 amount of heat is liberated which must be removed rapidly to avoid impairment of the activity of the contact mass. V

The widely different conditions prevailing during the reacting and regenerating periods present complex problems in constructing reaction chambers which will permit proper and effective control of both periods. I

One of the important objects of the invention is to provide an improved method of carrying' out catalytic reactions.

. Another important object of the invention is to provide an improved process for carrying out `lcatalytic reactions in which the catalyst mass is subjected to periodic regenerating treatment.

A further object of the invention is to provide an improved method of catalytic cracking of oils in which the vapors undergoing cracking are recycled through certain of the catalyst beds in the. cracking chamber.

. 1 is a vertical sectional view of the reaction chamber constructed in accordance with the invention.

Fig. 2 is a transverse sectional view taken alone.r

the line III-II of Fig. 1, and Fig. 3 is a transverse sectional view taken along the line III- III of o Fig. 1. Fig. 4 is a partly diagrammatic illustration of a more complete apparatus for cracking oil in which the reaction chambers shown in Fig. 1 are embodied. and Fig. 5 is a further modification of the apparatus constituting' one phase of the invention.

Referring to Figs. 1, 2 and 3, the reference number III designates a reaction chamber containing a plurality of vertically spaced beds of solid catalyst material, I2, I3, Il and I5, separated by vapor spaces I6, I'I and I8 respectively. Addi- .tional vapor spaces I 9 and 20 are provided at the bottom and top of the chamber. Communicating with the separate vapor zones are conduits 2l to 25 which may be used for the introduction or removal of gases from the chamber. For convenience, four separate catalyst beds are shown.

It will be understood, however, that'the invention is not restricted to this number as any desired number may be used. Each of the catalyst beds I2 to I5 is supported on a perforated grid Another more detailed object of. the invention4 plate 26, which is held in position by an inwardly extending circumferential flange 21 secured to thewall of the reaction chamber. To facilitate the introductionof the grid plates from the ends of the chamber, the grid plates are of a diameter slightly less than the inner diameter of the anges 21 and are locked in position after insertion by an intervening segmental ring 28 interposed between the grid plate and the iiange 21.

The reaction chamber is provided with a 1ongitudinal conduit 29 extending through the two upper beds of catalyst I4 and I5 and forming a y vapor passage between the top vapor zone 20 and the middle vapor zone I1.

A second longitudinal conduit 3| extends downwardly through the two lower catalyst beds I2 and I3 and forms a vapor passage between the lower vapor zone I9 and the middle vapor zone I1. A third conduit 32 extends through the two intermediate beds I3 and I4 and provides vapor communication between the upper intermediate vapor zone I8 and the lower intermediate vapor zone I6.

The vapor conduits 29, 3| and 32 are each provided with outwardly extending circumferential supporting flanges 33, 34 and 35 respectively, intermediate their ends, engaging the grid plates 26. By supporting the conduits intermediate their ends in this manner, the conduits are free to expand or contract longitudinally in both directions with varying temperature conditions.

The conduits 29, 3| and 32 are provided with removable closure valves 36, '31 and 38 respectively, which, when closed, as shown in Fig. 1 will prevent the passage of vapors through the respective conduits. Valves 36 and 31 are operated by a valve stem 39 which extends downwardly through the stuiiing box 4| at the top of the reaction chamber and terminates in the upper end of the conduit 3| The valve stem 39 projects through central openings in the valve plates 36 and 31 and is maintained in axial alignment with the conduits 29 and 3| by guides 42 and 43 positioned within the conduits. The central openings in the valve plates 36 and 31 are somewhat larger in diameter than the valve stem to form a loose fit therebetween. Positioned below the closure plates 36 and 31 are ferrules 44 and 45 respectively, rigidly secured to the valve stem 39 adapted to lift the closure valves upon raising the valve stem.

This construction permits the closure plates to seat themselves properly on the vapor conduits regardless of any slight warping or misalignment of the valve stem and the ferrules may be caused to impart a hammer blow to the closure plates and insure loosening them even though, the formatherebetween.

Closure valve 38 for vapor conduit 32 is likewise operated by a valve stem 48 extending through a conduit 49 extending through the upper catalyst 'bed I5 and through stuiling box 5I in at the top of the reaction chamber.. The closure valve 38 is mounted on the valve stem 48 and operated in The conduit 49 has a permanent closure plate 52l `welded or otherwise connected therewith which is provided with a central opening through which valve stem 48 extends. The conduit 49 is preferably of the same diameter as the vapor con duits 29, 3| and 32.

The bottom catalyst bed is likewise provided with a blank conduit 53 of the same diameter as vapor conduits 29, 3| and 32 and is provided with a plate 54 to prevent the passage of vapors therethrough.

By providing blank conduits 49 and 53 passn: through the upper and lower beds I2 and I5 respectively, each of the catalyst beds will have the same volume of catalyst per unit depth. Consequently, when the catalyst beds are of uniform l depth eachcatalyst bed will have the same rethe same manner as closure plates 36 and 31. 75

sistance to the ow of gases therethrough. This is of particular importance when the gases are caused to pass through the separate beds in parallel, such as during the regenerating period as hereinafter described. To insure that all of the beds are of uniform depth, a bench ring 55 secured to the interior wall of the chamber is provided for each catalyst bed.

As shown in Figure 1, a heat exchange coil 56 may be located in each of the vapor zones I6 to 2|) respectively, for supplying or removing heat during the process. Thus, during the cracking period, additional heat may be supplied to compensate for that lost by the cracking reaction. During the regenerating period, heat may be extracted by passing a cooling fluid through the coil. The exchange coil may, if desired, be positioned in the catalyst beds rather than in the vapor zones or may be omitted and the temperature otherwise controlled.

By the above construction, gases may be introduced into the catalyst chamber at a single Point, passed through the separate catalyst beds in series or in parallel and withdrawn at a single point from the reaction chamber. For example, by operating valve stems 39 and 48 to close valve plates 36, 31 and 38 and by closing valves in conduits 22, 23 and 24, gases may be introduced at one end-of the reaction chamber, through conduits 2| or 25, passed successively through each catalyst bed and withdrawn from the opposite end. By opening valve plates 36, 31 and 38 and closing valvesl in conduit 2|, 25 and 24, gases may be introduced through central conduit 23 communicating with the central vapor space I1. A portion of the gases so introduced may pass downwardly through the lower intermediate catalyst bed I3, and may discharge through conduit 22. Another portion may pass upwardly through the upper intermediate catalyst bed I4, then downward through conduit 32 to the outlet conduit 22. A further portion of the gas may pass directly upward through vapor conduit 29 to the upper end of the chamber and thence downwardly through the top catalyst bed I5 and thence through conduit 32 to the discharge conduit 22 and the nal portion may pass downwardly through vapor conduit 3| thence upwardly through the lowest catalyst bed I2 after which it will combine with gases passing through the lower intermediate bed and will discharge through outlet conduit 22. By closing valve in conduit 22, and opening valve in conduit 24, the gases may be discharged through conduit 24 rather than 22. It will be apparent that the ow of gases may bethe reverse of that just described, namely, the gases may be introduced either through conduits 22 or 24 and discharged through 23. Also gases may be introduced to the chamber through the top or bottom conduits and after passing in parallel through the several beds be discharged through intermediate conduits 22 or 24 or vice versa. For example, gases may be introduced through the upper conduit 25 and then take the following path. A portion may pass directly down through the upper bed l and discharge through conduit 24 or continue through conduit 32 and discharge through conduit 22. The remainder of the gases will pass through the upper vapor conduit 29, tothe central vapor space l1 from which a portion will pass upwardly through the upper intermediate catalyst bed I4, another portion downwardly through the lower intermediate bed I3 and the remainder will pass through the lower vapor conduit 3| and thence upwardly through the lower bed l2 and discharge through conduits 22 or 24. Likewise the gases may be passed into the chamber through the lowest conduit 2l, and, after passing in parallel through the respective catalyst bed, withdrawn either through conduits 22 or 24 or vice versa.

It will thus be apparent that the gases may be optionally introduced through any one of the conduits, passed in parallel through the beds and then withdrawn through any one of the other ports except of course that the gases cannot be introduced through one .port and withdrawn through another p0rt in direct communication with the entrance port by the internal vapor conduits. In'each ofthe ilows above described in which a parallel arrangement is obtained the gases pass in opposite directions through adjasingle catalyst bed. The construction thus Drovides a simple and flexible means vfor permitting the gases to iow either in series or in parallel through the various catalyst beds.

In order to reduce the regenerating period to a minimum and thus reduce the time in which the reaction chamber is out of operation, itis desirable to pass the necessary volume of regenerating gases through the catalyst in the shortest possible time. However, the resistance of lthe catalyst mass to the passage of gases therethrough varies y directly with kthe `square of the velocity of the gases. By dividing the regenerating gases and the time of contact of the gases with the catalyst mass which, for a reaction chamber of given dimensions, is determined by the linear velocity of the gases and the depth of catalyst through which they pass. The desired degree of conversion or in other-words.. yield of desired end products can depth of catalyst mass for a given linear velocity or linear velocity of gases for a given depth of catalyst. As a practical matter, hmveveryit is desirable to impart a minimum linear velocity to the gases suiilcient to insure uniform distribution of the gases throughout the full cross-sectional area of the catalyst in all beds. To obtain the required time of contact without reducing the linear velocity below the desired minimum,.the gases to be reacted may be passedin series through the separate beds.

According to .another phase of the invention, the gases to be reacted are passed through the separate beds in parallel and the required contact time is obtained at higher gas velocities by continuously recycling a portion of the products withdrawnfrom the chamber as hereinafter described. i

The reaction chamber above described may be used in various types of treatments involving a1- ternate treatment in the presence of a solid contact mass and regeneration of the mass in the same reaction chamber. It is ofparticular application, however, in the cracking ot hydrocarbon oil and a diagrammatic illustration ofthe apparatus suitable for carrying out the -cracking is shown in Fig. 2.

Referring now to Fig. 4, the oil to be cracked is introduced into the system through line 60 provided with a pumpSl whichvforces the oil to the heating coil 82 llocated in the furnace 83. The

" from unvaporized residue. The residue so separated is withdrawn through line B6. Steam may be injected into the bottom of the tower, as shown, to assist vaporization of the oil.v The vapors after passing in contact with contact plates 61 for removal of entrained solids and liquids pass overhead through line 68 to a second heating coil 89 in furnace 10. The vapors during their passage through heating coil 69 are heated to a temperature which may range from 700 to 1G00" F.

depending upon the character of the stock being treated.

The oil vaporsaiter being heated to the desired reactiontemperature pass through transfer line 'Il having branch lines I2 and 12' merging with conduits 2l and 2| respectively leading into the bottom of reaction chambers Il) and l0' respectively. These reaction chambers are duplicates and are constructed as previously described. For convenience, prime numbers will be employed to distinguish the like elements in chamber I and "further alternative, the fresh charging stock may be controlled therefore by'modifying either the 75 be heated to the desired reaction temperature within the rst heating coil 82 and after passing through the combined separator and fractionating tower 85 for separation of unvaporized constituents, the vapors may be passed directly to the reaction chambers through by-pass line 15 without being passed through the second heating coil 69.

Branch lines 12 and 12 leading to reaction chambers I8 and I8' respectively, are provided with valves 11 and 11', so that the heated vapors may be passed to either reaction chamber as desired. For purpose of description, it will be assumed that the cracking operation is being carried out in reaction chamber I8 while regeneration is being accomplished in chamber I8', it be- 88 then pass to a receiver I8| wherein the liquid ing understood that each reaction chamber is alternately on the cracking and regenerating operation. Assuming that cracking is being accomplished in` chamber I8, valve 11' in branch 12' will be closed and valve 11 in line 12 will be open. Also valves 19, 88 and 8| in conduits 22, 23 and 24 leading from chamber I8, will be closed, valve 82 in line 25 leading from the top of reaction-chamber I8 will be open and valve plates 36, 31 and 381m the internal vapor conduits (see Fig. 1) will be closed to prevent transfer of vapors therethrough.

The heated vapors pass upwardly through successive catalysts beds I2, I3, I4 and I5. 'I'he cracking catalyst may be of any type capable of bringing about the desired cracking reaction. By way of example hydrosilicates of alumina which are naturally active or which have been made active by suitable treatment, such as with acid may be employed to advantage, also synthetic gels consisting principally of silica and alumina may be employed. The time of contact of the oil vapors with the catalyst will depend upon the nature of catalyst used, the temperature maintained, the desired degree of conversion and other factors. In general, the time of contact may be of the order of from .15 to 5.0 volumes of liquid feed per volume of catalyst per hour. The oil after being subjected 'to the desired degree of cracking in the reaction chamber I8 is withdrawn through conduit 25 and passes through line 88 to a fractionating tower 81. A heat exchanger 88 may be provided in line 86 for partially cooling the cracked products before introducing the same into the fractionating, tower 81. For example, the products may be cooled to a temperature ranging from 550' to '100 F.

The vapors introduced into the fractionating tower 81 are subjected to fractionation to condense insuiciently cracked constituents as reiiux condensate. Liquid condensate formed in the fractionating tower 81 may be withdrawn from the tower through line 88 and may be removed from the system through line 9| or recycled to the heating coilv82 through line 92 and pump 93.

` In lieu of withdrawing the total liquid products from the fractionating tower 81 through line 88 as described, the tower 81 may be provided with a trap out tray 94 communicating with line 85 whereby a lighter condensate fraction may be removed from the process through line 98, or it may be recycled through lines 81, 92 and pump 93 to the inlet side ofthe heating oil coil 82 for further cracking treatment.

Vapors remaining uncondensed in the fractionating tower 81 pass overhead through line 88 to a condenser 88 wherein constituents boiling withinA the desired motor fuel boiling range are condensed. The products from the condenser condensate separates from uncondensed vapor constituents. Gases' separated in the receiver |8| pass through line |82 provided with a valve |83 which may be employed for imposing any desired back pressure on the fractionating tower 81 and catalyst chambers I8 and The pressure within the reaction chambers is preferably at substantially atmospheric except for the required back pressure to maintain the desired ilow although a mild superatmospheric pressure of the order of 50 to 100 pounds per square inch may be used.

The gases removed through line |82 may be passed to a suitable recovery system for the removal of low boiling gasoline constituents. The liquid condensate collected in the receiver |8| is withdrawn therefrom through line passed to a storage tank (not shown) as a nal distillate product of the process. This distillate may be subjected to any additional nishing treatment such as acid treating, clay treating, sweetening, hydrogenation or stabilization, or any combination of these` treatments for conversion into the nal finished motor fuel. A portion of the condensate withdrawn from the receiver |8| may be returned through line |85 to the top of the fractionating tower 81 as reilux therefor.

While the cracking operation is being carried out in the reaction chamber I8 as herelnbefore described, the catalyst contained in the reaction chamber I8' is subjected to regeneration to remove or burn of! carbonaceous deposits formed during the cracking operation.

During regeneration, valve 82' in branch line 86', valve 8|' in line 22 and valve 11' in line 12 will be closed while valve 88' in line 23' and valve 18' in line 24 will be open.

The catalyst is regenerated by the introduction of an oxidizing gas, for example, a mixture of air and diluent gases, such as steam or spent combustion gases. 'I'he regenerating gas is introduced into the system by means of a blower |86 which forces the regenerating gas through line |81 merging with branch lines |88 and |88' connected with lines 23 and 23 of chambers I8 and I8'.

The regenerating gas before being introduced into the reaction chamber I8 through the inlet conduit 23' is iirst preheated as hereinafter described to a temperature sufficient to initiate combustion of the solid carbonaceous deposits contained on the surface of the catalyst.

During regeneration, the internal valve plates 38', 31' and 38' in chamber I8' corresponding to valve plates 38, 31 and 38 in chamber I8 are in raised position so that the regenerating gases are caused to pass in parallel through the several beds of catalyst material positioned in the chamber as hereinbefore described.

The combustion gases resulting from regeneration are withdrawn from chamber I8 through outlet conduit 28' connected with manifold line These gases may be rejected from the system through valved line ||2 but are preferably used as a diluent for the oxidizing gas. To this latter end, the gases from manifold III', preferably pass to a reservoir I I3 provided with a vent ill. The vented gases from line |I2 or Ill may be sent to a heat recovery system such as a waste heat boiler (not shown) or to pressure turbines or both for recovery of energy therefrom.

The gases to be employed as a diluent are with- |84 and drawn Ifrom reservoir H3 through line IIS. The gases so withdrawn after being reduced in temperature, such as by the introduction of a quenching medium, i. e., water through line I6, or after passing through a suitable heat exchanger (not shown) are forced by means of a blower ||1 to admlx with fresh regenerating gas introduced by blower |06 thereby suitably preheating it.

When the cracking operation in chamber has reached a point where it becomes desirable to regenerate the catalyst and the catalyst in chamber I0' has been suiliciently regenerated, the chamber |0 is disconnected from the cracking circuit and interconnected with the regenerating circuit and the chamber I0 disconnected from the regenerating circuit and connected with the cracking circuit by reversal of the valves v hereinbefore described.

from a cracking operation to regeneration and vice versa may be accomplished for example in the following manner.

When the catalyst contained in the chamber l0' has been sufciently regenerated, the air supply introduced by means of pump |06 is dis'- continued and inert gases, such as steam or combustion gases obtained during the regenerating operation, are continuously circulated through the chamber i0 -by means of a circulating pump ||1 to remove residual oxygen retained in the chamber |0'. In lieu of employing steam or other inert gases for purging the chamber of residual oxygen, the chamber mayv be connected to a vacuum pump through suitable lines not shown and the purging accomplished by evacuation. When this is accomplished valves 19' and 80' are closed and valve stems 39' and 48' are lowered closing internal valve plates 36', 31' and 38' previously described, thus connecting the several catalyst beds in chamber |0' in series. Valve 11' in line 12 and valve 82 in line 86 are closed, disconnecting chamber |0 from the cracking circuit and the fractionating equipment. Simultaneously, valve 11' in line 12 and valve 82' in line 86 are opened thus connecting chamber |0' with the cracking circuit and fractionating equipment. Valve stemsl 39 and 48 in chamber I0 are then raised lifting valve plates 36, 31 and 38, opening internal conduits 29, 3| and 32, thus interconnecting the several catalyst bed in chamber |0 in parallel. Valve 18 in line 83 and valve 80 in line 84 are then opened connecting chamber |'0 with the regenerating circuit., Before introduction of the air into the regenerat-` ing circuit for commencing the regeneration,

'chamber l0 is purged of residual oil vapors by passing inert gas, such as steam, through the chamber or evacuating it as hereinbefore described. The residual oil vapors removed from chamber I0 during the purging treatment are preferably fractionated by suitable fractionating equipment (not shown) to recover the `oil constituents therefrom.

When the oil vapors have been completely purged from the chamber |0,.regeneration of the chamber is begun as herembefore described with reference to chamber l6.' f W.

The amount of air introduced into the regener-` ating gases is regulated to control the temperature maintained during the regeneration.

As described., the apparatus illustrated in Fig. 4 is adapted primarily for direct series ow of oil lvapors to be cracked and parallel flow of regenerating gases through the reaction chamber.

The apparatus lends itself readily, however,

to parallel flow of both cracking and regenerating gases or to intermediate recycling of the oil vapors to be cracked. Such a system is illustrated in Fig. 5. For simplicity, the vaporizing equipment has been omitted from Fig. 5, it being understood that the equipment shown in Fig. 4 or any suitable apparatus may be employed for vaporizing the oil and for bringing it to the required reaction temperature. The reaction chambers shown in Fig. 5 are of the same construction as in Figs. 1 and 4 and bear the same reference characters. The system illustrated in Fig. 5, however, has been modiiedto permit more flexible control of the oil vapors to be cracked. According to the modification shown in Fig. 5, a part of the gases passing through the reaction chamber are withdrawn through the side conduits, subjected to additional heating and returned to the reaction chamber. shown, the heat of the regenerating gases withdrawn from another chamber may be employed for supplying additional heat to the oil vapors being recirculated to the-reaction chamber.

Referring to Fig. 5, the oil vapors to be cracked after being vaporized and heated to the desired reaction chamber in suitable apparatus, not shown, are introduced into the system through line |20 from whence they may pass through line |2| having a valve |22 to a manifold line |23, having valved branch lines |24 and |25 leading to the bottom of reaction chambers l0 and |0' respectively. i

As distinguished from the mode of operation described in connection with Fig. 4 the external valves 19, 80 and 8| in conduits 24, 23 and 22A respectively, of reaction chamber |0 and valves 18', 80 and 8|' in corresponding lines 24', 23' and 22' of reaction chamber I0' remain open during the cracking period and oil vapors are continuously removed, heated and. recirculated back to the reaction chamber. It will be noted that lines 24 and 22 leading from reaction chamber I0 and corresponding lines 24 and- 22' leadingfrom reaction chamber I0 connect to a common manifold so Vthat the oil vapors may be withdrawn from either or both these lines during the cracking period as later described.

According to this modincation, lines 24 and 22 leading from reaction chamber |0 communicate with line |26 having a valved branch line |21 leading to a heat exchanger coil |28 located Within a heat exchanger |29 and another valved i branch line |30 leading to space surrounding the heat exchange coil |28. Products from the heat exchange coil |28 pass through line |32 to the suction side of a blower |33 which forces the oil vapors through a return line |34 having valved branch line |36 leading through line |36 to line 23 communicating with the central part of the reaction chamber |0 and another valved branch line |31 connecting with line |36 merging with line 23' leading to the central part ofl the reaction chamber I0'. l

Lines 24' and 22' interconnect with line |39 having a valved branch line |40 connecting with the inlet side of the heat exchange coil |28 and another valved lbranch line |4| connecting with the space surrounding the heat exchange coil |28.

line |46 connecting with line |36 between the valve thereof and the line 84 leading to chamber |0. Another valved branch line |41 interconnects line |45 with line |38 communicating with line 84 leading to chamber l0'.

Regulated amounts of air, to control regeneration temperature, are introduced into the gases cycled to the chamber undergoing regeneration through line |48 connecting with line |42 on the suctionside of the blower |44. Also, if the regenerating gases recycled to the regenerating chamber are insufliciently cooled during passage through the heat exchanger |29I they may be further cooled either by cooling coils, not shown, or by direct injection of steam or water through line |49.

The system as above described makes it possible to utilize blower |33 for recirculating vapors undergoing cracking and blower |44 for circulating regenerating gases to either of the two reaction chambers as desired. Assume, for example, the chamber is on the cracking stream whereas chamber I0' is undergoing regeneration. In such case, the valves in branch lines |30, |31, |40 and |46 are closed and valves in branch lines |21, |36, |4| and |41 are open.

Oil vapors withdrawn through either or both conduits 22 and 24 of chamber I0 pass through lines |26 and |21 to the heating coil |28 in heat exchanger |29 where they are further heated by regenerated gases from chamber I0'. The oil vapors after passing through the heat exchange coil |28 are withdrawn through line |32 connected to the suction side of blower |33 which i forces them through lines |34, |36 and 84 to the chamber |0 through central port 23.

Meanwhile regenerating gases are withdrawn from chamber I0' through either or both conduits 24' and 22' 'and pass through lines |39 and branch line |4I, to the space surrounding the heat exchange coil |28. If desired, additional air may be added at this point to burn any carbon monoxide that may be present in the regenerating gas. The regenerating gases on passing through the heat exchanger give up part of their heat to the `oil vapors passing through the heat exchange coil |28. The combustion products emerge from heat exchanger |29 through line |42. Excess gases over and above that required for preheating and diluting the air the desired amount are vented from the system through line |43. The remainder, with or without additional cooling, after being blended with the required amount of air to effect controlled regeneration is forced by means of blower |44 through line |45, branch line |41 and line |38, to central conduit -23' of reaction chamber l0'.

In lieu of adding additional air through line |48, all the required amount of air may be added to the regenerating gases entering the heat exchanger |29.

When it is desired to crack in chamber I0' and regenerate in chamber |0, the position of the valves above described will be reversed. It will be understood that both after the cracking and regenerating periods the chamber will be purged of residual gases either by steam or evacuation as described with reference to the process illustrated in Fig. 2 before changing over to the other period.

When chamber I0' is on the cracking stream and chamber I0 is undergoing regeneration, re-

exchange coil |28. From heating coil `|28 the heated vapors pass through line |32, blower |33, line |34, branch line |31, line |38 and line 84( back into reaction chamber I0.

Meanwhile, regenerating gases emerge from chamber I0 through either or :both ports 24 and 22 to line |26.' From line |26 they are conducted through branch line |30 leading to the space surrounding the heat exchanger coil |28, in which they passl in heat exchange relation with heat exchange coil |28. VFrom heat exchanger |29, the products pass through |42 and after venting excess gases through line |43 and combined with required amount of air are forced by blower |44 through line |45, branch line |46,

line |36 and 64 back into reaction chamber I0.

In its broader phases, the invention is not restricted to eectingheat exchange between the regenerating gases and recirculating oil vapors. 'I'he invention in its broader aspects contemplates other methods of heating the recirculating gases and other methods of extracting heat from the regenerating gases.

Returning now to the cracking operation, the apparatus illustrated in Fig. 5 permits a'flexible control of the cracking treatment involving a number of modes of operation.

When recirculating a portion of the vapors undergoing cracking as heretofore described, the internal valves may be maintained opened or closed during theA cracking operation, or valve plates 36 and 31 opened and valve 38 closed or vice versa.

According to one mode of operation illustrated in Fig. 5, the oil to be cracked is introduced into the bottom of the reaction chamber through the charge lines |20, |2|, |23, and then lthrough either |24 or |25. The cracked product.

after undergoing the desired conversion, may be passed from the reaction chambers to the fractionating tower 81 through lines 86 or 8 6'. When operating in this manner with internal valves closed, valve 8| in outlet conduit 22 and valve circulating oil vapors exit through either or both in conduit 23 leading into the central section of the reaction chamber may be opened so that a portion of the vapors after passing through the initial catalyst bed is Withdrawn from the chamber, passed through the heating coil |28 andretumed to the reaction chamber through line 23.

The cracked vapors after being reintroduced into the central section of the reaction chamber will divide, a portion passing downwardly through the lower intermediate catalyst bed and the remainder passing upwardly through the upper intermediate catalyst bed. Further recirculation may be obtained by opening valves 19 in outlet line 24 leading from the -vapor vzone 'disposed betweenY the top and upper intermediate catalyst bed. When this valve is opened a portion of th'e vapors after passing through the upper intermediate catalyst bed will continue through the upper catalyst bed from whence they will pass through lines 25 and 80 to the fractionatlng tower 81. The relinder of the vapors will be withdrawn through line 24 and recycled through the heating coil -|28. When operating in this manner, the vapors l to be cracked must first pass through the lower catalyst bed before being subjected to recirculation through the heating coil and all of the vapors passing to the fractionating tower 81 must pass through at least three catalyst beds.

In lieu of recirculating vapors from both linesv 22 and 24 valve 8| may be closed and valve 14 opened. In this case, the fresh vapors must pass through the three lower beds before being recirculated. In such case, recirculation is accomplished only through the upper intermediate catalyst bed.

When valve. 8| is open and valve-19 closed, recirculation is accomplished only through the lower intermediate catalyst bed.

Rather than having both valves 19 and 8| opened, either one of the two may be closed and the internal valve 38 in conduit 32 (see Fig. l) may be opened, thus providing communication between the lower intermediate vapor zone I6 and upper intermediate vapor zone I8. In such case, recirculation is accomplished in both intermediate catalyst beds.

As a further alternative, all of the internal valves within the reaction chamber may be maintained open during the cracking operation. According to this mode of operation, recirculation of the vapors is accomplished throughout all four of the catalyst beds. When operating in this manner, the relative volume of gases being recirculated as compared with the amount of gases being introduced into the reaction chamber should be so high that only a negligible amount of the fresh vapors are llay-passed directly through the catalyst chamber through internal ducts 29 and 3|.

Instead of introducing the vapors to be cracked into the bottom of the chamber, a part or all .may be introduced into the recirculating circuit through line |50 connecting charge line |20 with line |32 on the suction side of the blower |33. If additional heating of the charge vapors is desired, the fresh oil vapors may be passed through line communicating with line |21 on the inlet side of the heating coil |28. Also in lieu of. passing the cracked products from the top It will be understood that the products into-` duced into the fractionating tower will be abjected to the desired fractionation and subsequent treatment as set forth in more detail in the description of Fig. 4.

For simplicity, only two chambers have been l illustrated for carrying out the alternate reaction and regeneration treatment. In practice. however, it will be understood that any desired number may be employed depending on the required capacity of the equipment and the relative time involved in the reaction period as compared with that necessary for regeneration and purging the chambers before and after the regenerating operation.

While the apparatus has been described with reference to the catalytic cracking of hydrocarbon oil, it will be understood that it vwill have a more general application, such as. for example, the filtration of hydrocarbon oils. the clay treatment of cracked distillates, catalytic reforming Having thus described the preferred embodil ment, it is understood that this invention embraces such other variations and modifications as come within the spirit and scope thereof. It will also be understood that in the accompanying claims, it is the intention to claim all novel features of the invention as broadly as the art will permit. i

We claim:

1. A method of catalytic cracking of hydrocar' bon oil to produce lower boiling hydrocarbons 4which comprises heating the hydrocarbon oil to vaporizing and reaction temperature, introducing the resulting vapors into a reaction vessel providedv with a, plurality of horizontally extending catalyst beds arranged one above the,

other in spaced relation and including a top'bed,

a bottom bed and intermediate beds, passing theintroduced vapors through certain of said catalyst beds in series, withdrawing at least a por- I tion of the vapors undergoing cracking after they have passed through at least one catalyst bed and passing at leasta portion thereof through one of said intermediate catalyst beds and passing the remaining portion of the withdrawnv vapors first through a different intermediate bed and then through the last bed of catalyst and then o ut of said reaction vessel.

2. A method according to claim 1 wherein the withdrawn vapors are further heated before being returned to said reactionvessel.

3. A method of catalytic cracking of hydrocarbon oil to produce lower` boiling .hydrocarbons which comprises heating the hydrocarbon oilto vaporizing and reaction temperature, introducing the resulting vapors into the bottom of a reaction vessel provided with a plurality of horizontally extending catalyst beds arranged one above the other in spaced relation and including a top bed, a bottom bed and intermediate beds, passing the vapors upwardly through said bottom catalyst bed, withdrawing substantially all of the vapors undergoing cracking after they have passed through said bottom bed and Passing at least a portion of the' withdrawn vapors'through one of said intermediate beds and then mixing them with the vaporous products which have passed through said bottom bed and passing at least a portion of the remaining withdrawn vapors through said top catalyst bed. 4. A method according to claim 3 wherein the withdrawn vapors are further heated before being returned to said reaction vessel.

5. A method according to claim 3 wherein at least a portion of the withdrawn vapors is mixed with hydrocarbon vapors to be cracked and the mixture passed through said bottom' bed.

vQLHARLES W. TYSON. EGER V. MURPEREE. HERBERT G. M. FISCHER. 

